It is proposed to study the mechanism by means of which L-threonine is decarboxylated to the vitamin B12 component 1-amino-2-propanol in a model system which requires the presence both of a corrinoid and of a thiol compound. If sufficient progress is made the experience gained will be used to return to the enzyme system, first described in this laboratory, which utilizes L-threonine as a source of the 1-amino-2-propanol moiety of the vitamin. A new purification of NMN deamidase has yielded the pure enzyme. The mechanism of action of this enzyme in terms of its dissociation into two dissimilar subunits will be studied. The study of a novel pathway for the formation of delta-aminolevulinic acid from delta-ketoglutaric acid by an extract of corn leaves will be continued. BIBLIOGRAPHIC REFERENCES: Lohr, J.B., and Friedmann, H.C., Biochem. Biophys. Res. Commun. 69, 908-913 (1976): New Pathway for delta-Aminolevulinic Acid Biosynthesis: Formation from alpha-Ketoglutaric Acid by Two Partially Purified Plant Enzymes. Ford, S.H., and Friedmann, H.C., Arch. Biochem. Biophys. 175, 121-130 (1976): Vitamin B12 Biosynthesis: In Vitro Formation of Cobinamide from Cobyric Acid and L-Threonine.